By the way, as I said, I have two engines - gasoline and electric. First was the gasoline and then I put the electric. as it turned out, I have both activated. i.e. when you put a new engine the system makes it active, regardless of the engine type and availability of fuel, but does not deactivate the other motors when they are on board. then system are checking all engines for the presence of fuel. If even one of them out of fuel, the system will not start, and the usual access to the controls of key ^ are blocked.
Maybe we need that installation of the new engine does not make it automatically active. only if it is one aboard.
and do we really need to be able to run all engines at once? I have them two now, four in plans. Is it logical to simultaneously work all engines aboard? What about fantastic transmission in this way?)